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Hi @Kristen Scott,
Good day, and I appreciate the clear details of your concern and the thorough reproduction steps.
Based on what you shared, the behavior you’re seeing is consistent with how SharePoint Online calendars/events render date/time values when a site’s regional time zone is configured specifically, the calendar view is treating the site regional time zone as the authoritative time zone for display, rather than converting the event time to each viewer’s user/profile time zone (including DST adjustments for the viewer).
A - What’s happening
1/ The calendar is rendering using the site’s regional time zone
Your site is configured with the regional setting (UTC) Dublin, Edinburgh, Lisbon, London. Although it includes the “UTC” label, this is not a fixed UTC (no‑DST) time zone. It follows UK/Ireland rules and observes Daylight Saving Time (BST).
As a result, SharePoint calendar displays event times based on the site’s time zone, rather than converting them to the viewer’s Central/Eastern time zone.
2/ Why the Graph-created event displays as 6:00-7:00 PM
The event was created using UTC timestamps (17:00-18:00 UTC). On April 21, the Dublin/London time zone is in DST (UTC+1), so the calendar displays:
- 17:00 UTC > 18:00 (6:00 PM) site time
- 18:00 UTC > 19:00 (7:00 PM) site time
This matches the observed behavior. The data sent via Graph is valid UTC; the difference comes from site-time-zone-based rendering.
3/ Why the SharePoint UI-created event also shifts
When events are created using the SharePoint date/time picker, the entered time may be interpreted and stored relative to the site time zone, and the calendar then renders it again using that same site time zone. As a result, events entered expecting Central time (for example, 12:00-1:00 PM) may appear later, because the calendar does not consistently apply the viewer’s profile time zone.
More info here: Change regional settings for a site - Microsoft Support
B - Practical workarounds
Below are approaches customers commonly use depending on the desired outcome:
Option 1 - If the calendar should display in a single “business” time zone
Please set the SharePoint site regional time zone to the intended business time zone (e.g., Central or Eastern).
This ensures the calendar shows times consistently for everyone in that standard.
Note: Not per-user localization
Option 2 - If the requirement is per-user time zone rendering (Central/Eastern per viewer)
SharePoint Events/Calendar views (especially in modern experiences) may not reliably render times per viewer’s profile time zone.
If per-user localization is a strict requirement, recommended alternatives include:
- Using Outlook/Exchange calendars for scheduling across time zones (designed for per-user time zone and DST handling)
- Implementing a custom front-end (e.g., SPFx / Power Apps) that explicitly converts and displays times in the viewer’s time zone
- This option may require adoption of Exchange calendar or custom UI
Option 3 - Store “reference” time zone details alongside the event (Optional)
If you need to keep SharePoint as the storage location, you can add supporting fields like:
- “Original time zone” (e.g., Central)
- “Local start time (text)” for clarity
- Or a computed display pattern in a custom view/page
Note: More data/UX complexity
For additional information, you or (your IT department) can refer to this article: Date and Time Column Behavior in SharePoint List/Library
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C - Contact Microsoft Support
If the issue persists even after these steps, it may stem from a deeper system-level cause. In this case, I recommend contacting your organization's IT administrator, who can submit a support request to Microsoft through the Microsoft 365 Admin Center. They’ll be able to access system-level information to investigate the issue thoroughly and provide assistance. At the very least, they can offer the most effective workaround to ensure your experience remains smooth and secure.
As community moderators, we appreciate your understanding that we do not have access to the administrative tools or permissions required to investigate or modify these configurations. We also do not have the capability to initiate remote sessions for direct assistance. Our role is to guide users to the appropriate resources and support channels.
I hope this information is helpful. Should you have any further questions or need additional assistance, feel free to reach out.
I look forward to hearing your thoughts on this.
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